| 摘要 |
To achieve both cost reduction and strength enhancement of a cage by appropriately managing, at the time of forming pockets through a punch-pressing process in a base material made of medium-carbon steel, a size of a secondary fracture portion formed in a shear surface of the base material. Provided is a cage (5) for a constant velocity universal joint, the cage being formed by forming, in a peripheral direction of a cylindrical base material (6) made of medium-carbon steel, pockets (5c) for accommodating torque transmission balls (4) through a punch-pressing process, and hardening the entire base material (6) through quenching, the cage (5) including a shear surface (5c2) left in at least part of each of the pockets (5c) as a result of the punch-pressing process, the shear surface (5c2) including a secondary fracture portion (7) that is formed therein at a time of the punch-pressing process and exhibits a wedge-like shape in cross-section orthogonal to the shear surface (5c2), in which, in the secondary fracture portion (7) in the cross-section orthogonal to the shear surface (5c2), a segment (AB) is 1.0 mm or less in a case where a secondary-fracture distal end portion is represented by A and a foot of a perpendicular from the secondary-fracture distal end portion to the shear surface (5c2) is represented by B.
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